The present invention relates to a connection assembly for connecting two elongate elements at an intersection. Such connections are useful in various commercial applications where one element such as a tube or a rod is to be connected at an angle with another tube. Commercial applications would include the production of grids, fences, cages. Applications are also foreseen in the furniture and aircraft industries as well as in the packaging and transportation of freight.
The German Patent DE-C-33 44 351 discloses a grid arrangement wherein plate-like carrier rods are provided with oval holes therethrough. Cross-connector tubes are passed through the holes in perpendicular arrangement. After having passed through the holes, the tubes are mechanically deformed on either side of the hole to produce a connection at the intersection.
In many applications, it is desirable to have a lightweight construction but one of optimum mechanical strength. In such cases, it would be desirable to have a connection assembly at the point of intersection which can sustain high loads and which does not deteriorate under fatigue. Moreover, the volume taken up by the connection should be kept to a minimum to satisfy space requirements. The connection assembly, particularly when used to form a grid, should be simple and inexpensive to manufacture, but at the same time be reliable in terms of quality of the connection. Moreover, the connection assembly should be suitable for series production.
According to the present invention, a connection assembly is provided which satisfies the above criteria. The connection assembly comprises first and second elongate elements connected to one another at an intersection. The elements preferably are connected at right angles, although other angles are possible. The first elongate element has a receiving opening formed therein through which the second elongate element passes so as to penetrate through the first element. The first and second elements are then connected to one another at one or more positions within the region of their intersection. If the two elements are made of metal, the connection at the one or more positions may be performed by resistance welding. Alternatively, when the elements are made of plastic material, the connections can be made ultrasonic welding or induction welding. The connections can also be made by melt bonding or with an adhesive. As another alternative, the two elements may be appropriately deformed within the region of intersection so as to produce a form fit connection.
The inner diameter of the receiving hole of the first tube is preferably dimensioned with respect to the outer diameter of the second tube such that it passes therethrough by overcoming a slight frictional force. The second tube therefore has a non-positive (frictional) connection with the first tube when mounted. This arrangement provides for stability of the connection against bending forces which will arise at the intersection. Although this arrangement is preferred a frictional fit is not necessary for the present invention.
In another embodiment of the invention, the central axes of the two elements intersect one another and form a plane. The outer surfaces of the smaller diameter second element defines two tangential planes, which are both parallel to the plane defined by the centre axes of the two elements. The elements are connected to one another at two positions at these tangential planes, where the outer surface of the second element lies opposed to an inner surface of the first element.
In another preferred embodiment, the first element comprises a tubular structure and is provided with one or more ridges formed along its interior. The crests of these inner ridges will contact or lie close to the outer surface of the second element when penetrated through the receiving opening. The locations where the one or more ridges either contact or lie close to the outer surface provides the one or more contact positions.
The first and second elements used in constructing the present connection assembly can be of various shapes. For example, the first and second elongate elements can be provided in tubular form with a cross-section being substantially circular, oval, square, triangular or rectangular. In a further embodiment, the first element can be provided as an open profile, such as a U-shaped or a C-shaped profile with the receiving opening provided in the side legs of the profile. It is also possible that the second elongate element be provided in the form of a plate which passes through a corresponding slot in the first element as the receiving opening.
The connection assembly of the present invention provides good mechanical strength and reliability of the connection, while at the same time allowing a simple and inexpensive manufacturing process. In the case that the second element penetrates the first element in a frictional fit, additional stability against bending moments arising within the plane of the two elements is provided. The one or more positions at which the elements are then connected enhances the strength against deformation out of the plane of the two elements.